1. Field of the Invention
The present invention relates to a signal driving system, more particularly, a source driver for a display.
2. Description of the Related Art
Referring to FIG. 1, a scan driver 11 and a source driver 12 are utilized to control a liquid crystal display for showing image. For example, the scan driver 11 has 256 gate driving lines (G1, G2 . . . , G256) scanned in sequence to control the pixels of the liquid crystal display. The pixels are controlled by corresponding thin film transistors (TFT). The gate driving lines are connected to the corresponding gates of the corresponding thin film transistors, and control ON/OFF switching of the thin film transistors. The source drivers transmit driving signals to the corresponding thin film transistors, and control the gray scale and the brightness of the pixels so as to show image on the liquid crystal display.
Referring to FIG. 2, the conventional source driver 12 usually comprises a signal controller 121, a plurality of connectors 122, 124, and a plurality of driving devices 123, 125. The signal controller 121 receives signals from a host terminal e.g. computer terminal. The signals are processed by an analog/digital converting process, a proportion enlarged/decreased process, and a control signal is transmitted to the connectors 122, 124 by a timing control. The control signal is transmitted to the driving devices 123, 125 by the connectors 122, 124. The driving devices output driving signals to the corresponding thin film transistors according to the control signal.
The control signal of the conventional signal controller 121 is a Transistor Transistor Logic (TTL) signal having amplitude between 0-3.3 voltage. The Transistor Transistor Logic signal has the problem of easily induced electromagnetic interference (EMI). Therefore, the control signal of the signal controller 121 gradually changes to a Reduced Swing Differential Signal (RSDS) with a voltage between 1.1 and 1.3 volts (1.2±0.1 volts). The amplitude of the Reduced Swing Differential Signal is 0.1 voltage, and the Reduced Swing Differential Signal has no electromagnetic interference problem.
However, in the Chip on Glass (COG) and Wiring on Array (WOA) technique, because of the very small diameter of wires on the substrate and the material of the wires on the substrate, the resistance of the wires are very large to seriously decay the amplitude of the Reduced Swing Differential Signal. Therefore, the Reduced Swing Differential Signal cannot be transmitted on the driving devices 123, 125, and the driving devices 123, 125 cannot produce the corresponding driving signal.
Therefore, it is necessary to provide a signal driving system so as to solve the above problem.